1. Field of the Invention
The present invention concerns connectors that retain optical elements in axial abutting relation. More particularly, the present invention relates to a connector for buffered optical fibers which includes an elastically deformable, generally tubular housing adapted to receive a rigid mount having a generally elliptical cross-section. The housing has regions with specific geometries and elastic properties adapted to retain particular fiber components, e.g., a bare fiber terminal end or a buffer, against a channel in the elliptical mount. The varied geometries and elastic properties of the regions allow each region to open a predetermined distance when elastically deformed and to exert a predetermined level of compressive force against the mount when attempting to return to its undeformed state. The differential interaction between the regions of the housing and the mount allows highly precise insertion, alignment and retention of the bare fibers while, at the same time, allowing simple insertion, alignment and retention of the much larger and more diametrically-varied fiber buffers with an adequate but less exacting degree of precision.
2. Description of Related Art
Optical elements, such as optical fibers, laser diodes and other light sources, polarizers, lenses, beam splitters and the like, are presently in wide use, particularly for high speed communication and data transmission. Connectors may be used to non-permanently connect, disconnect and reconnect the optical elements incorporated into an optical communication network, while splices may be used to permanently connect the network elements. The present application is directed to connectors, which may be easily coupled and uncoupled to allow multiple, non-permanent connection and reconnection of optical elements.
Many such connector designs are in present use. However, regardless of the design selected for a particular application, alignment of the terminal ends of the connected optical elements is critical to maintain the signal strength as the light passes through the connection. To connect standard telecommunications grade optical elements, such as optical fibers, the fibers must be supported and oriented both longitudinally and transversely to minimize attenuation of the light signal passing through the fiber connection. As is well known in the art, this is accomplished by optimizing fiber positioning to ensure minimum transverse, longitudinal and angular offset between the fiber cores.
An optical fiber connector described in FIG. 4 of U.S. Pat. No. 4,470,180 to Blomgren shows a resiliently deformable housing 35 including first and second interior wall portions 36-37. An internal member 38 with an undercut 52 is positioned in the passageway proximate the first interior wall portion 36. If the housing is in a relatively undeformed state, an optical fiber 40 may be supported between the undercut portion 52 and the housing 35 and held firmly in position. If compressive force is applied to deform the housing as indicated by arrows 41, a second optical fiber or an optical device can be inserted to become coaxially interconnected with the first, or the first fiber may be easily removed from the connector.
In FIG. 1 of U.S. Pat. No. 4,729,619 to Blomgren, the deformable housing 16 contains a mandrel 24 with an alignment groove 26 having a substantially V-shaped profile to support the bare fibers 12, 14 to be connected. Rigid chocks 20, 22 with reception grooves 34, 36 are adapted to releasably secure the buffer coatings 38-39 of the fibers when inserted into deformable housing 16. When the housing 16 is in a relatively undeformed state, the bare optical fibers are urged into contact with the alignment groove 26 in the mandrel and held firmly in position between the mandrel 24 and the housing 16. The buffers of the optical fibers are urged into contact with the reception grooves 34, 36 of the chocks 20, 22 and held firmly in position between the chocks and the housing. If compressive force is applied to deform the housing, a second optical fiber or optical device may be inserted into the connector to axially interconnect with the first, or the first fiber may be easily removed from the connector.
The connectors described in the '180 and '619 patents require use of a small, pliers-like tool to deform the housing for insertion and/or removal of the optical fibers from the mount.
The connector in U.S. Pat. No. 5,078,467 to Blomgren may include a three-piece mandrel 21 consisting of a central ceramic portion 22 designed to retain the coaxially abutting bare optical fibers and a pair of resinous strain relief chocks 24 designed to retain the optical fiber buffers (See FIG. 2). In an alternate embodiment, the mandrel 31 is a one piece structure with a central shallow groove 33 to retain the abutting optical bare fibers and deeper outer troughs 35 to retain the buffers (see FIG. 3; see also EP 0 438 898). The mandrel is surrounded by an envelope 27 which incorporates a pair of normally parallel flanges 28 centrally divided into a pair of levers 28A. The housing may be integrally molded to the levers or may be a tubular structure emplaced between the lever arms. When the opposed levers are squeezed together, the housing is deformed and an optical fiber or optical device may be received or removed at the end of the connector.
Bare optical fibers, which typically have a diameter of 125 .mu.m.+-.1 .mu.m, are much smaller and manufactured to much closer tolerances than their buffers, which have a diameter of about 250 .mu.m.+-.15 .mu.m to 900 .mu.m.+-.50 .mu.m. The bare fibers must be aligned with a considerably higher degree of precision than the buffers, and must be retained against the mount with considerable force. These requirements were addressed in the Blomgren patents by concentrating on the properties of the mount-forming the mount for the bare fibers and the chock for the buffers from different pieces with separate material properties (see col. 2, lines 28-35 of the '467 patent). While generally effective, this approach requires use of many different pieces to make a single connection between optical fibers and/or optical elements. Forming a connection between fibers requires aligning the bare fibers in the grooved mandrel, and then inserting the chocks around the fiber buffers.
To ensure that precise connection of two optical fibers has, in fact, been made, the assembler would prefer to feel the bare fibers slide inward along the mount channel and abut one another. This precision "feel" is difficult to achieve with the multi-piece connectors described above, since the bare fibers must remain in place in the mount channel while the chocks are inserted into the housing to retain the buffers. The increased friction created as the large diameter buffers slide along the mount channel also masks the feel of the connector, and it may be difficult for the assembler to determine when a firm connection is made. The friction created during buffer alignment and lack of connector feel also may cause bending and/or breakage of the bare fibers.
Large variations in manufacturing tolerances between the bare fibers and the buffers, as well as the significant differences in the required degree of interconnection precision between them, are difficult to accommodate in a single tubular housing structure. When deformed, such a housing must have a geometry and elastic properties which allow insertion of the bare fibers and buffers into the mount channel and movement within the channel of the bare fibers into axial abutting relation. However, the housing must not deform to such a large extent that the bare fibers slip outside the channel during the insertion procedure. Further, the undeformed housing must have geometry and elastic properties to retain all components against the channel. A single housing material and structure which will satisfactorily perform each of these insertion, alignment and retention functions has not yet been identified.